1. Field of the Invention
The present invention relates to a heat transfer cell and assembly for a heat exchanger and methods of fabricating the same, and more particularly, to a heat transfer cell and assembly for a heat exchanger and methods of fabricating the same, capable of minimizing vortex at and in the inlet of a passage into and through which a fluid flows, increasing a contact area between the fluid and its contact plate to improve heat exchange efficiency, easily and rapidly fabricating an assembly by stacking a plurality of heat transfer cells to improve productivity, preventing welding defects resulting from downward sagging of the heat transfer plate when the heat transfer cells are stacked, reducing the number of whole constituent parts and the resulting fabricating costs, and improving assemblability.
2. Description of the Related Art
In general, heat exchangers are fluid-to-fluid heat recovery apparatuses that recover heat included in gases discharged to the outside in industrial facilities such as air-conditioning facilities and then supply the recovered heat to productive facilities or interiors of buildings.
These heat exchangers are designed to perform heat transfer (heat exchange) between a high-temperature fluid and a low-temperature fluid without a physical contact, and are classified into a plate type heat exchanger, a heat pipe type heat exchanger, a disc type heat exchanger, etc. according to the type of a heat exchange module that is an internal core part.
Among these heat exchangers, the plate type heat exchanger recovers heat by arranging a plurality of heat transfer plates in parallel to each other at predetermined intervals, adopting a gap between every two neighboring heat transfer plates as a channel through which a fluid flows in one direction, and alternately supplying a high-temperature fluid and a low-temperature fluid to the respective channels so as to perform heat transfer (heat exchange) through the respective heat transfer plates.
One example of the plate type heat exchanger is disclosed in Korean Patent Publication No. 1993-0702655 (Sep. 9, 1993). According to the plate type heat exchanger of this document, a rigid parallelepiped shaped core is installed in a frame, and the core is formed of a plurality of thin parallel plates that define alternating passages for two different fluid flows. Each of the thin parallel plates is connected to its adjacent plate by parallel bars alongside edges thereof, wherein each bar is of stronger construction than each plate. The frame includes a pair of spaced parallel plates and transverse structural connectors. Seal means are provided both between vertical comers and transverse comers of the core and the adjacent surfaces of the frame defined by the pair of plates and by the structural connectors.
However, in this related art, the plurality of thin parallel plates constituting the core are welded so as to define the fluid passages, i.e. first and second gas flow passages, intersecting at right angle via the plurality of vertical, horizontal bars. For this reason, a process of individually welding the bars to an inlet and an outlet between the adjacent plates disposed in parallel requires a high precision of welding, which further increases the burden of a worker and reduces work efficiency. Further, the number of constituent parts is increased to act as a main factor that increases fabrication costs.
Further, the core is assembled by repeating a process of horizontally disposing the first plate, a process of stacking the second plate on the first plate via the bars, and a process of welding the bars to the plates so as to have the first and second gas flow passages intersecting at right angle. When each plate made of metal is welded, the plate sags due to its own weight, which leads to a failure in welding.
In the case in which a heat transfer area of the plate is increased in order to meet design requirements of large facilities, a sagging amount of the plate is relatively increased in proportion to the heat transfer area of the plate. Thus, this welding failure acts as a factor that reduces product reliability.
Further, the first fluid and the second fluid flowing to the different passages of the core collide with a vertical front face of each bar installed at the inlet of the passage, so that fluid vortex and fluid resistance take place at the inlet of the passage, and so that a flow of the fluid flowing into each passage forms a turbulent flow rather than a laminar flow. For this reason, a contact area between the plate as the heat transfer member and the fluid is reduced, and thus heat exchange efficiency is reduced.
Meanwhile, when the heat is exchanged between the first and second fluids having different temperatures via the plate, one of the fluids which has an atmospheric temperature is typically subjected to the heat exchange by contacting the plate heated by the other fluid having relatively high temperature, for instance 200° C. or more. Thus, moisture can be created on a surface of the plate due to the temperature difference between the heated plate and the room-temperature fluid.
This moisture is mainly created at the inlet of the passage through which the fluid having the atmospheric temperature flows. The moisture acts as a main factor that corrodes the plate made of metal to reduce the lifespan of the product.